From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757527AbYJVSbR (ORCPT ); Wed, 22 Oct 2008 14:31:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753306AbYJVSbF (ORCPT ); Wed, 22 Oct 2008 14:31:05 -0400 Received: from mail-gx0-f29.google.com ([209.85.217.29]:32876 "EHLO mail-gx0-f29.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752476AbYJVSbE (ORCPT ); Wed, 22 Oct 2008 14:31:04 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=DEa8PNIUR1ltCVdP0/ja1JsT21gYpGsN2f93Fmnu+kZDWvRp90uCJgPBn4k+LX679v 8vyHj9qssR9LIvt60kVMsGm7J9Z/E44cp9mMHefuj3gO7o0XYIuPQPzsVThXbzZdAdaU c1Yd/CY1DCheE5kTtgYOJ6b0k7ivgAR5+Jvco= Date: Wed, 22 Oct 2008 22:30:55 +0400 From: Cyrill Gorcunov To: Christoph Lameter Cc: Pekka Enberg , LKML Subject: Re: [RFC] SLUB - define OO_ macro instead of hardcoded numbers Message-ID: <20081022183055.GN9639@localhost> References: <20081022163530.GH9639@localhost> <20081022165354.GI9639@localhost> <20081022172103.GJ9639@localhost> <48FF6800.20705@cs.helsinki.fi> <20081022175827.GL9639@localhost> <20081022181556.GM9639@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [Christoph Lameter - Wed, Oct 22, 2008 at 11:24:58AM -0700] > On Wed, 22 Oct 2008, Cyrill Gorcunov wrote: > >> [Christoph Lameter - Wed, Oct 22, 2008 at 11:10:56AM -0700] >>> On Wed, 22 Oct 2008, Cyrill Gorcunov wrote: >>> >>>> +#define OO_SHIFT 16 >>>> +#define OO_MASK ((1 << OO_SHIFT) - 1) >>>> +#define MAX_OBJS_PER_PAGE 65535 /* see struct page.objects */ >>> >>> This is == OO_MASK right? Otherwise things will break when we change >>> OO_SHIFT. >>> >> >> Yes, I set it 65535 directly to distinguish it from OO_MASK >> meaning not value and point to page.objects since they are >> u16. Which meant that is the point where all limits start. >> So it we set OO_SHIFT to say 14 it will not be a problem >> but if we exceed 16 bits it will break SLUB. Am I right? >> (I become scratching the head :) > > If you set it > 16 then the size of the field in struct page is violated. > > So > > #define MAX_OBJ_PER_PAGE MIN(1 << bits_in(page.objects) - 1, OO_MASK) > > ? > > Looks really good for me (if it worth anything). But Christoph doesn't OO_SHIT inspired by u16 too which means we could use MAX_OBJ_PER_PAGE in form you mentoined but maybe we should define #define OO_SHIFT bits_in(page.objects) to point out why we use 16 not 14, not 18 or whatever? How do you think? - Cyrill -